Journal Article

Effects of <i>anti</i>-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[<i>a</i>]pyrene on human small airway epithelial cells and the protective effects of <i>myo</i>-inositol

Harumi Jyonouchi, Sining Sun, Koji Iijima, Mingyao Wang and Stephen S. Hecht

in Carcinogenesis

Volume 20, issue 1, pages 139-145
Published in print January 1999 | ISSN: 0143-3334
Published online January 1999 | e-ISSN: 1460-2180 | DOI:
Effects of anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene on human small airway epithelial cells and the protective effects of myo-inositol

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Benzo[a]pyrene (B[a]P), a tobacco-derived carcinogen, induces lung tumors in rodents through its carcinogenic metabolite, anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (B[a]PDE). Tumorigenesis is inhibited by dietary myo-inositol in the post-initiation phase. However, little is known about how B[a]PDE and myo-inositol affect normal human lung cells. We addressed this question using untransformed human small airway epithelial (SAE) cells. SAE cell viability decreased <50% in parallel to an increase of apoptotic cells (>20%) 2 days after the cells were treated for 1 h with B[a]PDE (>100 nM). In contrast, the cell number and viability were not altered in A549 human lung cancer cells by B[a]PDE treatment up to 10 μM with <5% apoptotic cells and <10 U/l LDH in the medium. SAE cells retain the features of basal cells in serum-free, low Ca2+ (4 nM) medium up to 4–5 passages, but in serum-supplemented or serum-free, high Ca2+(1 mM) cultures, they differentiate into non-ciliated epithelial cells expressing Clara cell secretory protein (CCSP). A non-toxic, physiologically relevant dose of B[a]PDE (1 nM) partially inhibited serum and Ca2+-induced SAE cell differentiation. This effect was abolished by wortmannin, a phosphatidylinositol-3 kinase (PI-3K) inhibitor, and PD98059, a mitogen activated protein kinase (MAPK) kinase-1 (MEK1) inhibitor, but not by SB202190, a p38 MAPK inhibitor, or melittin, a protein kinase C inhibitor. Myo-inositol (10–100 μM) did not alter growth or differentiation of untreated SAE or A549 cells, but reversed the inhibitory effect of B[a]PDE on serum and Ca2+-induced SAE cell differentiation when supplemented to the culture after B[a]PDE treatment. This myo-inositol action was not altered by PD98059, wortmannin or melittin, but was partially suppressed by SB202190. Collectively, these results indicate that B[a]PDE inhibits serum-induced SAE cell differentiation, possibly involving activating signals through a PI-3K/MEK1 mediated MAPK pathway, whereas myo-inositol protects SAE cells against this inhibitory effect of B[a]PDE perhaps through both PI-3K/MEK1 and p38 MAPK pathways.

Keywords: B[a]P, benzo[a]pyrene; B[a]PDE, anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene; BSA, bovine serum albumin; CCSP, Clara cell secretory protein; DMSO, dimethyl sulfoxide; MAPK, mitogen activated protein kinase; PI-3K, phosphatidylinositol-3 kinase; RT, room temperature; SAE, small airway epithelial; SAPK, stress activated protein kinase.

Journal Article.  5375 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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